Motions in Dilute Acids on Amalgam Surfaces. 211 



usual, by saying u All these motions are rapidly consumed by 

 friction." 



It would be possible to determine by observations whether 

 any after-effects of former motions are still present in the 

 ocean. For this purpose it would only be necessary to insti- 

 tute comparative observations of the currents at the most va- 

 rious depths in the central portions of the great equatorial 

 currents and the region of calms. Yet we could not hope to 

 demonstrate small remnants of former motions with a certainty 

 like that with which this is possible in relation to the after- 

 effect of the former higher temperature of the earth by mea- 

 surements of subterranean temperatures. 



Further, those above-calculated numbers give a hint how 

 remote, at the least, we have to imagine the initial state to 

 have been from the present time, or for how long a period, at 

 the least, we must imagine that the trade-winds have blown 

 in their present extent and strength, to justify the assumption 

 that the present state of motion of the equatorial currents is 

 approximately stationary. For this about 100,000 years are 

 required if we take for a basis a mean sea-depth of 4000 metres 

 and take no account of the damping influence of the conti- 

 nents and islands, which must somewhat lessen that number. 



That every initial state, however, finally vanishes, and, from 

 the simple law of distribution laid down, gives place to a sta- 

 tionary one, is evident from the form of the series for w, and 

 has, besides, been shown generally for all temperature-problems 

 by K. von der Muhll*. 



Giessen, January 5, 1878. 



XXVII. Motions produced by Dilute Acids on some Amalgam 

 Surfaces. By Bobert Sabine")". 



IN the December (1876) Supplementary Number of the 

 Philosophical Magazine I stated an opinion, supported 

 by experimental evidence, that the motions which Erman, 

 Draper, and others have observed in certain electrolytic liquids 

 when in contact with mercury surfaces, and in the circuit of 

 an electric current, are due to displacements caused by oxida- 

 tion and deoxidation at different points. 



In following up the subject since, I have made further 

 experiments, and have noticed some phenomena which are in- 

 teresting (although perhaps of no practical value), to which, I 

 believe, attention has not hitherto been directed. 



* Math. Annahn, ii. p. 648. 



t Communicated by the Author. 



P2" 



